Little Whirlpool Ram's-horn Snail (Anisus vorticulus)
Key Details
| Taxonomic Groups: | Invertebrate > mollusc > Mollusc (non-marine) |
| Red List Status: | Vulnerable (Not Relevant) [VU(nr)] |
| D5 Status: | Included in the baseline Red List Index for England (Wilkins, Wilson & Brown, 2022) |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | Ramshorn Snail |
| UKSI Recommended Name: | Anisus (Disculifer) vorticulus |
| UKSI Recommended Authority: | (Troschel, 1834) |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | Seddon et al., 2014 |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | All of the GB population is in England where it is known from three SACs (1) Arun Valley, (2) Pevensey Levels and (3) Norfolk Broads. It appears to be stable in the Arun Valley (may even be increasing) but recent sound evidence of decline at Pevensey Levels ( a key national site). It is unknown how the population is currently faring in the Norfolk Broads. In many ways this species is conservation dependent, It is the 'most protected' non-marine mollusc in England as an EUHSD Annex IV species. |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | The species is heavily dependent on appropriate ditch management and is at risk of local extinctions if inappropriate management is undertaken. There is an NE landowner protocol in place to advise landowners if managing ditches on their land actually or potentially supporting the snail. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | Yes |
| Justification: | In addition to specific ditch management the snail benefits from 'landscape' scale issues like the maintenance of grazing at sites and the maintenance of water quality by avoidance of fertiliser imports. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 7. Best approach adopted at appropriate scales |
| Recovery potential/expectation: | Low - Relict or natural rarity |
| National Monitoring Resource: | Structured - sufficient |
| Species Comments: | This species may already be receiving sufficient conservation support in numerous ways and from a variety of governmental and NGO's. |
Key Actions
Key Action 1
Proposed Action: Maintain surveillance and periodic monitoring of the species in the 3 SAC's. Importantly, derive eDNA profiles of affixed diatom communities upon which Anisus feed, and establish a method to monitor their population in relation to different ditch management methods.
Action targets: 3. National Monitoring Plan agreed and implemented
Action type: Targeted monitoring
Duration: >10 years
Scale of Implementation: ≤ 10 sites
High priority sites: Arun Valley, Pulborough Brooks, Pevensey Levels, Norfolk Broads
Comments: Currently subject to intense monitoring due to Article 17
Key Action 2
Proposed Action: Provide advice and guidance to landowners to ensure all ditch management follows updated NE management protocol (annexe B of licence WML-CL14)
Action targets: 7. Best approach adopted at appropriate scales
Action type: Advice & support
Duration: >10 years
Scale of Implementation: ≤ 10 sites
High priority sites: Arun Valley, Pulborough Brooks, Pevensey Levels, Norfolk Broads
Comments:
Key Action 3
Proposed Action: Create spur ditches on adjacent or occupied ditches; a proven way to maintain population reserves when a ditch is being managed (as the spur area is left untouched and acts as a recolonisation population for the main ditch.
Action targets: 7. Best approach adopted at appropriate scales
Action type: Habitat creation
Duration: >10 years
Scale of Implementation: ≤ 5 sites
High priority sites: Arun Valley, Pulborough Brooks, Pevensey Levels, Norfolk Broads
Comments:
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.